By the end of this month, according to the Copenhagen Accord, all parties to the UN Framework Convention on Climate Change are due to report what cuts in emissions they will make by 2020. Broadly speaking, the Annex 1 parties, who will account for about half of global emissions over the period, will commit to reducing current emissions by 30% by 2020, or 15% on average in the decade between now and 2020.

Thus, if and only if every Annex 1 party to the Copenhagen Accord complies with its obligations to the full, today’s emissions will be reduced by around half of that 15%, namely 7.5%, compared with business as usual. If the trend of the past decade continues, with business as usual we shall add 2 ppmv/year, or 20 ppmv over the decade, to atmospheric CO2 concentration. Now, 7.5% of 20 ppmv is 1.5 ppmv.

We determine the warming forestalled over the coming decade by comparing the business-as-usual warming that would occur between now and 2020 if we made no cuts in CO2 emissions with the lesser warming that would follow full compliance with the Copenhagen Accord. Where today’s CO2 concentration is 388 ppmv –

Business as usual:                              ΔT = 5.7 ln(408.0/388) = 0.29  C°

–          Copenhagen Accord:           ΔT = 5.7 ln(406.5/388) =  0.27  C°

=          “Global warming” forestalled, 2010-2020: 0.02 C°

One-fiftieth of a Celsius degree of warming forestalled is all that complete, global compliance with the Copenhagen Accord for an entire decade would achieve. Yet the cost of achieving this result – an outcome so small that our instruments would not be able to measure it – would run into trillions of dollars.

For the rest of this article by Christopher Monckton, click here.